Short answers, pulled from the story.
The year 1861 marked the first time Prestwick Golf Club opened its Challenge Belt competition to both professionals and amateurs. Old Tom Morris won this inaugural open event while James Ogilvie Fairlie finished eighth as the best amateur player.
Tennis experienced a major change when the Open Era began in 1968. Grand Slam events started allowing both amateur and professional players to compete together from that point forward.
A significant policy shift occurred in 1986 when the IOC allowed international federations to decide eligibility rules. Professional athletes gained the right to compete alongside amateurs after this decision.
World Aquatics voted in 2022 to prohibit transgender athletes from women's elite competitions before creating an open category for athletes whose gender identity differs from their birth sex in 2023. This pilot project aimed to launch at the 2023 Swimming World Cup in Berlin but was cancelled due to a lack of entries.
Entrants to the 2025 U.S. Open golf tournament needed a USGA official handicap of 0.4 or less. Qualifying rounds reduce the field before reaching the final championship event while top ranked players often receive a bye directly into the main draw.